Related patent application Serial No. 94-29454, Korea, filed Nov. 7, 1994.
The present invention relates to high-fidelity sound reproducing systems and, more particularly, to systems of the type described in U.S. Pat. 5,327,505 which issued Jul. 5, 1994 in the name of the present inventor. In the systems described in the patent, the output transformers of a sound reproducing unit are mounted in a speaker module which is located at a position remote from the output amplifier of the sound reproducing unit.
As pointed out in the patent, it is usual in high-fidelity sound reproducing systems to use two or more speakers which cover complementary frequency ranges. Specifically, in two-speaker systems, a high-frequency speaker (tweeter or driver) and a low-frequency speaker (woofer) are provided with appropriate high-frequency and low-frequency bandpass filters with predetermined crossover characteristics. The systems are constructed so that audio output signals in the high-frequency portion of the frequency range are directed predominantly to the high-frequency speaker and audio output signals in the mid and low-frequency portion of the frequency range are directed predominantly to the low-frequency speaker.
In the prior art systems, the output from the output audio power amplifier of the sound reproducing equipment is supplied to a passive crossover network which separates the high and low frequencies, thereby supplying the mid and low frequencies to the woofer and the high frequencies to the tweeter or driver.
To achieve realism in sound reproduction systems fundamental conditions must be satisfied, namely: the frequency range must include without frequency discrimination all audible components of the various sounds to be reproduced; the volume range must permit noiseless and distortionless reproduction of the entire range of intensity associated with the sounds; and the reverberation characteristics of the original sound must be approximated in the reproduced sound.
It has been found difficult in the prior art sound reproducing systems to fulfill some of the fundamental conditions listed above without resorting to relatively complex and expensive circuitry, especially in cases where the speakers are located at a position remote from the output power amplifier of the sound reproducing equipment.
Such difficulties are overcome in the systems described in the patent by locating the output transformers and the high- frequency/low-frequency bandpass filters in a remote speaker unit displaced from the output audio power amplifier of the sound reproducing equipment, and then by connecting the audio power amplifier to the primary windings of the output transformers by appropriate electrical extension leads.
In systems described in the U.S. Pat. No. 5,327,505 referred to above there are no appreciable energy losses or changes in frequency characteristics due to the extension leads. The system of the patent also assures the complete separation of high and low-frequency signals from the output amplifier. This is because the separated signals are delivered directly to the speakers.
The systems of the patent also provides for the availability of completely independent volume controls for each speaker and assures distinct crossover characteristics for high and low-frequency components, and also for mid-frequency components if so desired.
For example, by overlapping frequencies independently, such as 20 Hz to 5,000 Hz for the low-frequency speaker, and 150 Hz to 20,000 Hz for the high-frequency speaker, faithful reproduction may be achieved, for solo performances of piano, violin and cello, for example, as well as for tenor and soprano singers.
Also, the systems of the patent preclude distortions in the mid-frequency range when the low-frequency filter is set, for example, to a range of 500 Hz to 4,000 Hz, with independent high-frequency separation for choruses, symphony orchestras, heavy metal music, etc. Specifically, the systems of the patent permit the control of crossover, and independent control of volume in each frequency range so as to adapt the reproduction characteristics of the systems to the sounds being reproduced.
In addition, overall efficiency is increased materially by the systems of the patent because separation of the frequency ranges occurs at the remote speaker unit rather than at the output amplifier. The overall result is that sound is reproduced by the speakers at a selected decibel level with less energy being required as compared with present-day systems.
The system of the present invention is of the same general type as the systems described in the patent. However, in the present system the multiple winding output transformers used in the systems described in the patent are replaced by autotransformers. This constitutes a distinct improvement in the quality of the audio signals delivered to the speakers. This is because the output transformers with separate primary and secondary windings produce distortions in the audio signals due to inductive changes in the multiple winding transformers as a function of frequency. Also, the autotransformers used in the system of the present invention are advantageous over the multiple winding transformers used in the systems of the patent because of the excessive wire requirements of the multiple winding transformers as compared with the autotransformers of the system of the present invention.